The present invention relates to a combined pneumatic and hydraulic pressure transducer, particularly a double acting pressure capsule having two cooperating pressure cylinders.
Such pressure transducers are known from Publication No. HB 43 603 DA of FAG Kugelfischer KgaA, the assignee hereof. Such transducers are used in so-called start-off assistance systems for automotive vehicles. Those systems prevent the spinning of the more poorly adhering drive wheel, for instance, on ice and snow. The pneumatic-hydraulic pressure transducer comprises a double-acting vacuum capsule with hydraulic cylinders flanged onto it. A vacuum pump produces a vacuum in one of the two chambers of the capsule and pressure in the other chamber. This shifts the diaphragm piston and acts on the hydraulic piston of the flanged-on hydraulic cylinder, which leads to a pressure buildup in the corresponding brake circuit. As a result, the faster turning wheel is braked.
In practice, it has been found that the pressure which can be produced with known pressure transducers is in many cases insufficient. A pressure transducer of large dimensions, which includes a diaphragm piston of larger diameter, requires more space, and space is very limited in modern passenger cars.